System method and apparatus for localized heating of tissue

• US 20030139788A1
• Filed: 12/05/2002
• Published: 07/24/2003
• Est. Priority Date: 01/18/2002
• Status: Active Grant

• Current Assignee: Apsara Medical Corporation
• Original Assignee: Apsara Medical Corporation
• Inventors: Eggers, Philip E., Ridihalgh, John L.
• Granted Patent: US 6,850,804 B2
• Time in Patent Office: Days
• US Class Current: 607/96
• CPC Class Codes: A61B 18/04 by heating by applying electromagnetic radiation A61B18/18; hyperthermia using electric or magnetic fields, radiation or ultrasound A61N
• CPC Class Codes: A61B 18/18 by applying electromagnetic radiation, e.g. microwaves radiation therapy A61N5/00
• CPC Class Codes: A61B 2017/00084 Temperature
• CPC Class Codes: A61B 2017/22002 preventing restenosis
• CPC Class Codes: A61F 2/82 Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents stent-grafts for tubular structures of the body other than blood vessels A61F2/04; stent-grafts for blood vessels A61F2/07; instruments specially adapted for placement or removal of stents or stent-grafts A61F2/95; for closing wounds, or holding wounds closed A61B17/04 - A61B17/115; dilators A61M29/00
• CPC Class Codes: A61F 7/12 Devices for heating or cooling internal body cavities
• CPC Class Codes: A61N 7/02 Localised ultrasound hyperthermia hyperthermia in general A61F7/00
• CPC Class Codes: G01K 7/38 the variations of temperature influencing the magnetic permeability

Abstract

System method and apparatus for accurately carrying out the in situ heating of a targeted tissue. Small implants are employed with the targeted tissue which exhibit an abrupt change of magnetic permeability at an elected Curie temperature. The permeability state of the implant is monitored utilizing a magnetometer. The implants may be formed as a setpoint temperature determining component combined with a non-magnetic heater component to enhance the tissue heating control of the system. With the system, a very accurate quantum of heat energy can be supplied to a neoplastic lesion or tissue carrying infectious disease so as to maximize the induction of heat shock proteins. The system also may be utilized in conjunction with non-magnetic arterially implanted stents for the hyperthermia therapy treatment of restenosis and in conjunction with the mending of boney tissue.

Claims

1. A method for thermally treating a target tissue volume within the body of a patient comprising the steps of:

(a) determining temperature value and treatment interval therapy data for carrying out said treatment of said target tissue volume;

(b) providing an untethered implant with a ferrite component formulated with oxides of Fe, Mn and Zn to exhibit a Curie point temperature corresponding with said temperature value and exhibiting a permeability attribute at temperatures below said Curie point temperature;

(c) providing an alternating current field based heating assembly having an on-state and an off-state and controllable for the generation of heat at said target tissue volume from an application component located externally of said body;

(d) providing a detector assembly having a magnetometer-based pick-up component positionable externally of said body and, when enabled, having a first detector output in the presence of magnetic flux lines of a magnetic field encountering said implant when exhibiting said permeability attribute and a second detector output in the absence of said permeability attribute;

(e) locating said untethered implant at an intra-body location effective for response to temperatures at the location of said target tissue;

(f) positioning said detector assembly pick-up at a location externally of said body effective for monitoring magnetic flux lines of said magnetic field encountering said implant;

(g) monitoring said detector assembly for the presence of said first and second detector outputs;

(h) controlling said heating assembly to have said on-state in response to said first detector output and to have said off-state in response to said second detector output; and

(i) controlling said heating assembly to terminate said generation of heat at said target tissue at the expiration of said determined treatment interval.

2. The method of claim 1 in which:

said step (b) provides said implant as a soft ferrite exhibiting a substantially repeatable permeability attribute discernibly affecting encountered magnetic flux lines when cycled from a temperature at said Curie point to a temperature below said Curie point.

3. The method of claim 1 in which said step (a) determines said therapy data to stimulate induction of therapeutic levels of heat shock protein from said target tissue volume.

4. The method of claim 1 in which:

said step (d) provides said detector assembly to derive said first detector output in response to the perturbance of magnetic flux lines of a said magnetic field which is the earth'"'"'s magnetic field and to derive said second detector output in the absence of said perturbance.

5. The method of claim 1 in which:

said step (g) monitoring said detector assembly includes the step;

(g1) commencing the timing of said treatment interval upon the occurrence of the initial said second detector output following said first detector output.

6. The method of claim 1 in which:

said step (e) locating said untethered implant at an intra-body location is carried out in the course of open surgery; and

said steps (b) through (d) and (f) through (i) are carried out subsequent to said step (e).

7. The method of claim 1 in which said step (a) determines said therapy data to effect hyperthermia therapy for the treatment of cancer.

8. The method of claim 1 in which said step (a) determines said therapy data to effect thermal therapy for the repair of boney tissue.

9. The method of claim 1 in which said step (a) determines said therapy data to stimulate induction of heat shock protein from a said tissue carrying infectious disease.

10. The method of claim 1 in which:

said step (d) for providing a detector assembly further comprises the steps of;

providing an oscillatory patient support; and

said step (g) further comprises the steps of;

positioning said patient upon said patient support; and

oscillating said patient support while maintaining said pick-up component in a stationary state.

11. The method of claim 1 in which:

said step (d) for providing a detector assembly provides said magnetometer-based pick-up component as a multi-channel pick-up array.

12. The method of claim 1 in which:

said step (h) controls said heating assembly by deriving said on and off states to provide a sequence of heating intervals; and

said step (g) carries out said monitoring by enabling said detector assembly for an interrogation interval occurring subsequent to a said heating interval.

13. The method of claim 1 in which:

said step (b) provides said implant as further comprising a non-magnetic heating component responsive to said alternating current field based heating assembly when in said on-state to elevate the temperature of said target tissue volume.

14. The method of claim 13 in which:

said step (b) provides said non-magnetic heating component in thermal exchange relationship with said ferrite component and configured with respect thereto to permit substantial encountering of said ferrite component with said magnetic flux lines.

15. The method of claim 14 in which:

said step (b) provides said untethered implant as further comprising a release agent material in thermal exchange relationship with said non-magnetic heating component and responsive for thermally activated dispersion when said ferrite component is at said determined temperature.

16. The method of claim 14 in which:

said step (b) provides said untethered implant with said non-magnetic heating component being provided as a stent having a generally cylindrically shaped outward luminal engagement surface, and said ferrite component is coupled in intimate thermal exchange relationship with said stent;

said step (a) determined data is determined to limit restenosis; and

said step (e) locates said implant within a blood vessel.

17. The method of claim 16 in which:

said step (b) provides said non-magnetic heating component stent as further comprising a release agent material supported in thermal exchange relationship therewith and responsive to effect its dispersion to limit restenosis when said ferrite component.

18. The method of claim 16 in which:

said step (b) provides said ferrite component as being coupled with said stent outward luminal engagement surface.

19. The method of claim 18 in which:

said step (b) provides said implant as further comprising a non-magnetic flexible band agalvanic with respect to said stent and surmounting said outward engagement surface and said ferrite component.

20. The method of claim 16 in which:

said step (b) provides an assembly of at least two of said ferrite components disposed generally along the lengthwise extent of said stent.

21. The method of claim 16 in which:

said step (e) for locating said implant locates said stent adjacent the heart of said patient;

said step (d) for providing a detector assembly provides said pick-up component as a single channel pick-up component; and

said step (g) monitors said detector assembly for the presence of said first and second detector outputs in conjunction with the beating heart driven movement of said implant

22. The method of claim 16 in which:

said step (g) carries out the monitoring of said detector assembly by determining said second detector output as the dimunition of perturbation of the earth'"'"'s magnetic field.

23. The method of claim 16 in which:

said step (d) for providing a detector assembly further comprises the steps of;

providing an electromagnet energizable to create a magnetic field; and

energizing said electromagnet to cause said magnetic field to extend through said target tissue volume; and

said step (g) carries out the monitoring of said detector assembly by determining said detector output as the diminution of perturbation of said created magnetic field.

24. The method of claim 16 in which:

said step (d) for providing a detector assembly further comprises the steps of;

providing an oscillatory patient support; and

providing said pick-up component as a single channel pick-up component;

said step (g) further comprises the steps of;

positioning said patient upon said patient support; and

oscillating said patient support while maintaining said pick-up component in a stationary state.

25. The method of claim 1 in which:

said step (a) determines said therapy data to effect hyperthermia therapy for the treatment of restenosis;

said step (b) provides said implant as an expandable, generally cylindrical non-magnetic support member having an outer surface extending along a central axis, having an insertion diameter of extent permitting its insertion within a non-magnetic stent previously implanted within a blood vessel of said patient and formed of bio-compatible material agalvanic with respect to said stent, said ferrite component being fixed in thermally responsive relationship with said support member.

said step (e) locates said implant within said previously implanted stent and causes it'"'"'s diametric expansion from said insertion diameter to an extent effective to interlock with said stent; and

said step (h) controls said heating assembly to cause the temperature of said stent to elevate toward said temperature value.

26. The method of claim 1 in which:

said step (a) determines said therapy data to effect an acceleration of the rate of repair of boney tissue incorporating a non-magnetic metal bone support component;

said step (b) provides said ferrite component in intimate thermal bond with said metal bone support component; and

said step (e) locates said implant in conjunction with the incorporation of said metal bone support component with said boney tissue.

27. The method of claim 1 in which:

said step (a) determines said temperature value as about 44.5°

C.; and

said step (b) provides said implant ferrite component as comprising a soft ferrite containing about 40 wt-% iron, about 15 wt-% zinc, about 9 wt-% manganese, and about 27 wt-% oxygen.

28. The method of claim 1 in which:

said step (a) determines said temperature value as about 44.5°

C.; and

said step (b) provides said implant ferrite component as formulated with about 51.8 mole percent iron oxide, about 20.1 mole percent manganese oxide, and about 28.1 mole percent zinc oxide.

29. An implant for employment in developing a thermotherapy setpoint temperature at a target tissue when disposed in thermal exchange relationship therewith, comprising:

a untethered soft ferrite component formulated with oxides of Fe, Mn and Zn to exhibit a Curie point temperature corresponding with said setpoint temperature, dimensioned for minimally invasive implantation at said target tissue, and having at least a portion of its outer surface exposed for interaction with the flux lines of an encountered interrogational magnetic field.

30. The implant of claim 29 in which said ferrite component exposed outer surface is coated with a biocompatible conformal layer.

31. The implant of claim 29 in which said implant further comprises:

a non-magnetic heater component in heat exchange relationship with said ferrite component and dimensioned with said ferrite component for effecting said minimally invasive implantation at said target tissue.

32. The implant of claim 31 in which:

said ferrite component and said heater component are each of generally semi-circular form having the semi-cylindrically defined flat surface of said ferrite component being coupled in said heat exchange relationship with the semi-cylindrically defined flat surface of said heater component.

33. The implant of claim 31 further comprising at least one tissue engaging implement fixed to and extensible outwardly from said heater component and effective to engage tissue in adjacency therewith when implanted.

34. The implant of claim 29 in which:

said soft ferrite component contains about 49 wt % iron, about 15 wt % zinc, about 9 wt % manganese and about 27 wt % oxygen and exhibits a Curie point temperature of about 44.5°

C.

35. The implant of claim 29 in which:

said soft ferrite component is formulated with about 49 wt % iron, about 15 wt % zinc, about 9 wt % manganese and about 27 wt % oxygen and exhibits a Curie point temperature of about 44.5°

C.

36. The implant of claim 31 in which:

said ferrite component is of generally cylindrical configuration; and

said heater component comprises at least one disk-like structure fixed to and extending outwardly from said ferrite component to an extent effective for anchoring said implant within adjacent tissue.

37. The implant of claim 31 in which:

said heater component comprises a discontinuity-containing covering of said ferrite component, said discontinuities exposing portions of said outer surface of said ferrite component of an extent effective for said flux line interaction.

38. The implant of claim 31 in which:

the surface at least of said heater component exposed to tissue supports a thermally activatable release agent.

39. The implant of claim 31 in which:

said ferrite component generally is configured having a surface disposed along an axis; and

said heater component is configured as a generally open, spiral sleeve positioned in thermal exchange relationship about said sensor surface and defining a generally helical-shaped open, outwardly exposed portion of said ferrite component.

40. The implant of claim 39 in which:

said ferrite component is configured in generally cylindrical form about said axis; and

said heater component is configured as a screw thread effective for anchoring engagement with adjacent tissue.

41. The implant of claim 39 in which:

said heater component sleeve is configured as a wire-like spiral structure having at least one end extending beyond said ferrite component forming a spirally-shaped tissue engaging implement.

42. The implant of claim 31 in which:

said ferrite component generally is configured having a surface disposed along an axis between first and second end portions; and

said heater component is configured comprising a first cap having a first cap end portion and a first sleeve portion mounted over said ferrite component first end portion and exposing a portion of said ferrite component surface.

43. The implant of claim 42 in which:

said heater component is configured further comprising a second cap having a second cap end portion and a second sleeve portion mounted over said ferrite component second end portion and exposing a portion of said ferrite component surface extending toward said first cap.

44. The implant of claim 31 in which:

said ferrite component comprises at least two ferrite portions having ferrite surfaces extending between inwardly disposed and outwardly disposed ferrite ends; and

said heater component comprises an intermediate heater sleeve supportably extensible over mutually adjacent said ferrite component ferrite surfaces at a location adjacent said inwardly disposed ferrite ends and exposing a portion of oppositely disposed ones of said ferrite surfaces.

45. The implant of claim 44 in which said heater component further comprises:

a cap end portion having a cap sleeve mounted over a said outwardly disposed ferrite end and exposing a portion of said ferrite surface extending toward said intermediate heater sleeve.

46. Stent apparatus for positioning within the body of a patient, comprising:

a metal stent structure having a contact surface configured for abutting engagement with tissue of said patient and formed of material responsive to an alternating field based energy applied externally of said body to elevate in temperature; and

an untethered sensor with a soft ferrite component assembly formulated with oxides of Fe, Mn and Zn to exhibit a Curie point temperature at a hyperthermia based level.

47. The stent apparatus of claim 46 in which:

said ferrite component is fixed to said stent structure contact surface.

48. The stent apparatus of claim 46 further comprising a flexible securement band agalvanic with respect to said metal stent structure and tensionally surmounting said metal stent structure and said ferrite component assembly.

49. The stent apparatus of claim 46 in which said ferrite component assembly is coated with a biocompatible electrically insulative conformal layer.

50. The stent apparatus of claim 46 in which:

said stent structure is generally cylindrically shaped; and

said ferrite component assembly comprises a first discrete ferrite component fixed to said contact surface, and a second ferrite component fixed to said contact surface at a location generally diametrically opposite from the location of said first ferrite component.

51. The stent apparatus of claim 46 further comprising a thermally activatable release agent coating extending over said metal stent structure, effective to limit restenosis when said stent structure is elevated in temperature.

52. The stent apparatus of claim 46 in which:

said ferrite component assembly comprises a soft ferrite containing about 49 wt % iron, about 15 wt %zinc, about 9 wt % manganese and about 27 wt % oxygen, said Curie point temperature being about 44.5°

C.

53. The stent apparatus of claim 46 in which:

said ferrite component assembly comprises a soft ferrite formulated with about 49 wt % iron, about 15 wt % zinc, about 9 wt % manganese and about 27 wt % oxygen and exhibits a Curie point temperature of about 44.5°

C.

54. A system for thermally treating a target tissue within the body of a patient comprising:

a tetherless implant located internally within said patient, positioned in thermally responsive relationship with said target tissue, having a ferrite component formulated with oxides of Fe, Mn and Zn to exhibit a Curie point temperature selected for carrying out said thermal treatment at a target temperature level, said ferrite component exhibiting a permeability of value perturbing the flux lines of a magnetic field at temperatures below said Curie point temperature;

a heating assembly actuable to apply alternating field based heat-inducing energy to said target tissue to an extent effective to elevate the temperature of said target tissue toward said target temperature level and de-actuable to terminate said application of thermal energy;

an implant monitor comprising a magnetometer with a pick-up located externally of said body in general adjacency with said target tissue, and, when enabled, having a first monitor condition in response to the perturbation of magnetic flux lines encountering said ferrite component when exhibiting said permeability at said value and having a second monitor condition in the substantial absence of said permeability at said value; and

a control assembly responsive to said first and second monitor conditions to actuate said heating assembly in a manner effective in a manner effective to attain said target temperature level at said target tissue.

55. The system of claim 54 further comprising:

a tetherless heater implant located internally within said patient in thermal exchange relationship with said target tissue and responsive to said heating assembly applied heat inducing energy to elevate the temperature of said target tissue in adjacency therewith toward said target temperature level.

56. The system of claim 55 in which said heater implant is formed of non-magnetic material.

57. The system of claim 54 in which:

said control assembly is responsive to said first monitor condition to actuate said heating assembly for a first interval of time, is responsive at the termination of said first interval of time to de-actuate said heating assembly and to enable said implant monitor, and is responsive to defer dis-enablement of said implant monitor and associated actuation of said heating assembly in the presence of said second monitor condition.

58. The system of claim 54 in which:

said control assembly is responsive to said first monitor condition to actuate said heating assembly for a first interval of time, is responsive at the termination of said first interval of time to de-actuate said heating assembly and to enable said implant monitor for a second interval of time less than said first interval of time, and is responsive at the termination of said second interval of time in the presence of said first monitor condition to actuate said heating assembly for said first interval of time.

59. The system of claim 54 in which said magnetic field is the earth'"'"'s magnetic field.

60. The system of claim 54 in which:

said implant further comprises a heater component having a geometrically volumetrically defined shape effective for untethered implantation at said target tissue, formed of non-magnetic material and located in adjacency with said ferrite component.

61. The system of claim 54 further comprising:

an oscillatory support for said patient; and

said magnetic field is the earth'"'"'s magnetic field.

62. The system of claim 54 further comprising:

an oscillatory support for said patient; and

an electromagnet having poles positioned to establish a said magnetic field within a region interruptible by said implant.

63. The system of claim 54 in which:

said implant monitor magnetometer pick-up is of a multi-channel variety.

64. The system of claim 54 in which:

said ferrite component is formulated with about 51.8 mole % iron oxide, about 28.1 mole %, zinc oxide, about 20.1 mole %, manganese oxide and oxygen and exhibits a Curie point temperature of about 44.5°

C.

65. The system of claim 54 in which:

said ferrite component contains about 49 wt % iron, about 15 wt %, zinc, about 9 wt % manganese and about 27 wt % oxygen and exhibits a Curie point temperature of about 44.5°

C.